Problem: Simplify the expression. $(-6z^{3}+5z)(5z^{2}-4z)$
Answer: First use the distributive property. $ - 6 z^3 (5 z^2) - 6 z^3 (-4 z) + 5 z (5 z^2) + 5 z (-4 z) $ Simplify. $-30z^{5}+24z^{4}+25z^{3}-20z^{2}$